class Solution
{
public:
    int countVowelStrings(int n)
    {
        vector<int> dp(5, 1);
        for (int i = 1; i < n; ++i)
        {
            partial_sum(dp.begin(), dp.end(), dp.begin());
        }
        return accumulate(dp.begin(), dp.end(), 0);
    }
};